NFL deals are fun to dream up, but in reality the trade market is a slippery slope, writes Scouts Inc.'s Keith Kidd.

Why aren't there more trades in the NFL? It's a fair question, but not an easy one to answer.
There are some obvious reasons more trades don't happen, but there also are some more complicated ones that might be overlooked by the average fan. It makes it so moves like Roy Williams being traded from Detroit to the Cowboys is more the exception than the rule.

Here are the biggest factors that keep more teams from making deals.

The salary cap. Finding a trade partner might seem simple enough for a team with a desirable or gifted player who, for whatever reason, simply no longer is a good fit. But making the numbers work under the cap often is an extremely complex problem that can be far more trouble than it's worth, especially when considering in-season trades. Because of prorated signing bonuses and salary accelerations, taking on a player with multiple years left on his contract can severely limit a franchise's flexibility to sign (or re-sign) players in the future. And by the time the regular season rolls around, many clubs don't have enough room under the cap to take on even the last few months of a significant contract.

Free agency and the draft. Since 1993, when the league went to a truly free market, player movement has increased and trades haven't been as necessary. Why bother haggling with another team over a single player when there's a deep pool of available options to choose from every offseason? And because a team willing to part with a talented, high-character player with a favorable contract situation usually is in rebuilding mode, the price often is steep: draft picks. In today's NFL, draft picks are gold. Teams simply aren't willing to give up a primary source of affordable labor. (After the top picks, the NFL draft actually works pretty efficiently, moneywise.)

And because a team's fortunes can turn on one nasty hit, it's impossible to know what kind of pick (or picks) a club is getting or giving up in any deal. What looks like a high second-round pick today may turn out to be a low second-rounder on draft day if your trade partner happens to have a run of bad luck.

Finding a taker. We all like to put on our GM hat from time to time, but most of the trade scenarios that get bounced around at the watercooler or on talk radio are long shots. NFL personnel men tend to be very cautious of situations that involve taking on another team's unwanted player, no matter how valuable an asset that player might appear to be. Because of the amount of information available nowadays, an interested team is bound to find negatives when scouting a potential target. And because today's trade game is more about pay than play, few personnel men are willing to risk compromising their cap to take on some other club's problem.

Richard C. Lewis/Icon SMIThe Chargers hit the jackpot in the Chris Chambers deal, but most teams are wary of trades going bust.

The system. Those who believe more in-season NFL trades could and should happen often point to last year's deal that sent Miami WR Chris Chambers to San Diego. And it was a great deal, for both teams -- but it was also a perfect storm that is hard to re-create. Chambers had become a luxury for a bad Dolphins club, and injuries had created a need that the receiver could fill for the Chargers. San Diego, a loaded team that believed it was just one player away, was willing to pay the cost of a second-round pick (which the team correctly anticipated would come at the end of the round). The cap numbers worked. Easy, right?

But what sealed the deal was Chambers' familiarity with coach Norv Turner's schemes. The two had previously worked together in Miami, so Chambers was familiar with Turner's terminology and passing tree. Also, the trade was pulled off on the Tuesday before San Diego's bye week, allowing Chambers to get acclimated to his new surroundings and get up to speed with any changes in the offense. Maybe it wasn't exactly a once-in-a-lifetime swap, but the chances of circumstances falling into place that open up a flood of similar trades are slim to none.

The position. It's critical. This isn't basketball or baseball, where one-on-one play or smaller games within the games frequently determine outcomes. In the NBA, you find a way to fit a guy who scores 25 points a night into your lineup. There's position flexibility in basketball, and smaller rosters mean a star player can make a greater impact. Some of that also applies to baseball, where a front-line pitcher can step in and play for a new team without missing a beat. But how does that translate in the NFL? Usually it doesn't. Can, say, a defensive tackle move between similar 4-3 schemes during the season and have an impact? Maybe. But can a quarterback move to a new team in Week 7, pick up a new scheme, establish a rhythm with his receivers and immediately take over a leadership role? Impossible. Folks hoping to see Browns backup QB Brady Quinn playing in another uniform this season are dreaming.

Depth. Though a critical injury can open the door for an NFL trade, teams are reluctant to deal for the same reason. One injury can compromise a team's depth at a position. Two can ruin it. Should the Raiders deal one of their trio of talented running backs, as has been rumored lately? It makes some sense on paper, but what happens if you deal RB Michael Bush and something happens to RB Darren McFadden? Now only an injury to creaky RB Justin Fargas stands between a productive running game and a weekly game plan that relies on the arm of inexperienced QB JaMarcus Russell. Things change too quickly in the NFL. Taking chances with your depth is playing with fire.

Morale. It's difficult enough to sign a player in the offseason and give him what he needs -- mostly time -- to adapt to his new surroundings. But trade for a player during the season, and you risk disrupting chemistry -- an important aspect of any NFL club. And what about the team that deals away a high-profile player? What message does it send to the guys in the locker room he leaves behind? If players believe management is packing it in, or if a restless fan base senses ownership giving up on a season, things can get ugly very fast.

The dynamics of any potential NFL trade are going to be complex, and now the decision-making process brings even more cooks into the kitchen. When I arrived in the league, a trade discussion involved the owner, coach, GM and maybe a few personnel men. It was a small room. Now? You have cap gurus, agents, vice presidents of player personnel, directors of football operations the list goes on. And the chances of someone offering an opinion that winds up shooting down the whole deal are raised.

In the end, most teams crave the kind of financial and roster flexibility the draft and free agency provide. The NFL trade market isn't dead, but most clubs have plenty of reasons to avoid it like the plague.

Scouts Inc. watches games, breaks down film and studies football from all angles for ESPN.com.